offroading

[Matt19]

guys silly question, but still I need answered. Last week I was trapped in a crowd of people, and the only way out was a nice hill that my h3 can easily scale. It was more of a test offroading experience. What I like to know is what are the meaning and differences of all the 4wd options.
what is the up arrow lock mean and down arrow lock, (low lock, high lock?) and when should they be used. Mud? uphill? down hill?

Funny thing is, I asked the firemen and officer there if i could go up the hill, it wasnt an even hill. It was a little rocky, and jagged. But they said "if you think you can, go ahead" but they didnt know i had a hummer. They just stood there and watched, just in aww. It wasnt even hard, i need more of a test now.